FIELD OF THE INVENTION
[0001] The present invention is directed toward a high pressure scroll compressor. More
particularly, the present invention is directed to a scroll machine which include
biased scroll members to handle the high axial forces created in the high pressure
scroll compressor.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] A class of machines exists in the art generally known as "scroll" machines for the
displacement of various types of fluids. Such machines may be configured as an expander,
a displacement engine, a pump, a compressor, etc., and the features of the present
invention are applicable to any one of these machines. For purposes of illustration,
however, the disclosed embodiments are in the form of a hermetic refrigerant compressor.
[0003] Generally speaking, a scroll machine comprises two spiral scroll wraps of similar
configuration, each mounted on a separate end plate to define a scroll member. The
two scroll members are interfitted together with one of the scroll wraps being rotationally
displaced 180° from the other. The machine operates by orbiting one scroll member
(the "orbiting scroll") with respect to the other scroll member (the "fixed scroll"
or "non-orbiting scroll") to make moving line contacts between the flanks of the respective
wraps, defining moving isolated crescent-shaped pockets of fluid. The spirals are
commonly formed as involutes of a circle, and ideally there is no relative rotation
between the scroll members during operation; i.e., the motion is purely curvilinear
translation (i.e., no rotation of any line in the body). The fluid pockets carry the
fluid to be handled from a first zone in the scroll machine where a fluid inlet is
provided, to a second zone in the machine where a fluid outlet is provided. The volume
of a sealed pocket changes as it moves from the first zone to the second zone. At
any one instant in time there will be at least one pair of sealed pockets; and where
there are several pairs of sealed pockets at one time, each pair will have different
volumes. In a compressor, the second zone is at a higher pressure than the first zone
and is physically located centrally in the machine, the first zone being located at
the outer periphery of the machine.
[0004] Two types of contacts define the fluid pockets formed between the scroll members,
axially extending tangential line contacts between the spiral faces or flanks of the
wraps caused by radial forces ("flank sealing"), and area contacts caused by axial
forces between the plane edge surfaces (the "tips") of each wrap and the opposite
end plate ("tip sealing"). For high efficiency, good sealing must be achieved for
both types of contacts.
[0005] One of the difficult areas of design in a scroll-type machine concerns the technique
used to achieve tip sealing under all operating conditions, and also at all speeds
in a variable speed machine. Conventionally, this has been accomplished by (1) using
extremely accurate and very expensive machining techniques, (2) providing the wrap
tips with spiral tip seals, which, unfortunately, are hard to assemble and often unreliable,
or (3) applying an axially restoring force by axial biasing the orbiting scroll or
the non-orbiting scroll towards the opposing scroll using compressed working fluid.
[0006] The utilization of an axial restoring force first requires one of the two scroll
members to be mounted for axial movement with respect to the other scroll member.
When the compressor is designed as a high pressure compressor to compress a refrigerant
like carbon dioxide, additional demand is placed on the axial biasing system as well
as the other components of the scroll compressor.
[0007] US 6,457,948 discloses a compressor according to the precharacterising section of claim 1.
[0008] The present invention provides a compressor according to claim 1, which is designed
to effectively compress carbon dioxide for a refrigeration system. The scroll compressor
of the present invention can include shorter and thicker scroll vanes and an orbiting
scroll member which is axially biased against a fixed scroll member. A vapor injection
system can be added to the scroll compressor to increase its capacity if desired.
In addition, the scroll compressor can be fitted with an oil injection system for
cooling and lubrication if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention will become more fully understood from the detailed description
and the accompanying drawings, wherein:
Figure 1 is a vertical cross section of a scroll compressor in accordance with the
present invention;
Figure 2 is an enlarged view of the scroll members of the scroll compressor illustrated
in Figure 1 showing the biasing system;
Figure 3a is an enlarged view of the biasing system illustrated in Figure 1;
Figure 3b is an enlarged view of a biasing system in accordance with another embodiment
of the present invention;
Figures 4a-4c are plan views of the scroll members and the biasing system illustrated
in Figure 3a;
Figure 5 is an enlarged view of the scroll members of the scroll compressor illustrated
in Figure 1 showing the pressurization port;
Figure 6 is an enlarged view of the scroll members of the scroll compressor illustrated
in Figure 1 showing an optional vapor injection system;
Figures 7a-7c are plan views of the scroll members and the vapor injection system
illustrated in Figure 6;
Figure 8 is an enlarged view of the scroll members of the scroll compressor illustrated
in Figure 1 showing an optional high pressure oil biasing system;
Figure 9 is a side cross-sectional view of an oil pressure regulator used for the
optional oil pressure biasing system for the compressor illustrated in Figure 8;
Figure 10 is an enlarged view of the scroll member of a scroll compressor in accordance
with another embodiment of the present invention;
Figure 11a is a plan view of a force diagram for the orbiting scroll member of the
present invention;
Figure 11b is a side view force diagram for the orbiting scroll member taken along
the radial axis;
Figure 11c is a side view force diagram for the orbiting scroll member taken along
the tangential axis;
Figure 12 is a plan view illustrating the trajectory of the forces on the orbiting
scroll member illustrated in Figure 10;
Figure 13 is a side cross-sectional view of the orbiting scroll member illustrated
in Figure 10;
Figure 14 is a plan view of the orbiting scroll member illustrated in Figure 10;
Figure 15 is a side cross-sectional view of the non-orbiting scroll member illustrated
in Figure 10;
Figure 16 is a plan view of the non-orbiting scroll member illustrated in Figure 10;
Figure 17 is a side cross-sectional view of the main bearing housing illustrated in
Figure 10;
Figure 18 is a plan view of the main bearing housing illustrated in Figure 10;
Figures 19a-19d illustrate the relationship between the passages, the recesses and
the sealing lip for the scroll compressor illustrated in Figure 10;
Figure 20 illustrates the relationship between the pressure within the recesses during
orbiting of the orbiting scroll member;
Figure 21 illustrates a side cross-sectional view of an orbiting scroll member in
accordance with another embodiment of the present invention;
Figure 22 illustrates a plan view showing an orientation of the recesses of the non-orbiting
scroll member in accordance with another embodiment of the present invention;
Figure 23 illustrates a side view cross-section of a scroll compressor in accordance
with another embodiment of the present invention; and
Figure 24 is a plan view, partially in cross-section showing the oil pressure ports
illustrated in Figure 23.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The following description of the preferred embodiment(s) is merely exemplary in nature
and is in no way intended to limit the invention, its application, or uses.
[0011] Referring now to the drawings in which like reference numerals designate like or
corresponding parts throughout the several views, there is shown in Figure 1 a scroll
compressor in accordance with the present invention and which is designated generally
by reference numeral 10. Compressor 10 comprises a generally cylindrical hermetic
shell 12 having welded at the upper end thereof a cap 14 and at the lower end thereof
a plurality of mounting feet 16. Cap 14 is provided with a refrigerant discharge fitting
18. Other major elements affixed to shell 12 include a lower bearing housing 24 that
is suitably secured to shell 12 and a two piece upper bearing housing 26 suitably
secured to lower bearing housing 24.
[0012] A drive shaft or crankshaft 28 having an eccentric crank pin 30 at the upper end
thereof is rotatably journaled in a bearing 32 in lower bearing housing 24 and a second
bearing 34 in upper bearing housing 26. Crankshaft 28 has at the lower end a relatively
large diameter concentric bore 36 that communicates with a radially outwardly inclined
smaller diameter bore 38 extending upwardly therefrom to the top of crankshaft 28.
The lower portion of the interior shell 12 defines an oil sump 40 that is filled with
lubricating oil to a level slightly above the lower end of a rotor 42, and bore 36
acts as a pump to pump lubricating fluid up crankshaft 28 and into bore 38 and ultimately
to all of the various portions of the compressor that require lubrication.
[0013] Crankshaft 28 is rotatively driven by an electric motor including a stator 46, windings
48 passing therethrough and rotor 42 press fitted on crankshaft 28 and having upper
and lower counterweights 50 and 52, respectively.
[0014] The upper surface of upper bearing housing 26 is provided with an annular recess
54 above which is disposed an orbiting scroll member 56 having the usual spiral vane
or wrap 58 extending upward from an end plate 60. Projecting downwardly from the lower
surface of end plate 60 of orbiting scroll member 56 is a cylindrical hub having a
journaled bearing 62 therein and in which is rotatively disposed a drive bushing 64
having an inner bore in which crank pin 30 is drivingly disposed. Crank pin 30 has
a flat on one surface that drivingly engages a flat surface (not shown) formed in
a portion of the bore to provide a radially compliant driving arrangement, such as
shown in Assignee's U.S. Letters Patent
4,877,382. An Oldham coupling 68 is also provided positioned between orbiting scroll member
56 and upper bearing housing 26 and keyed to orbiting scroll member 56 and upper bearing
housing 26 to prevent rotational movement of orbiting scroll member 56.
[0015] A non-orbiting scroll member 70 is also provided having a scroll wrap 72 extending
downwardly from an end plate 74 that is positioned in meshing engagement with wrap
58 of orbiting scroll member 56. Non-orbiting scroll member 70 has a centrally disposed
discharge passage 76 that communicates with discharge fitting 18 which extends through
end cap 14.
[0016] Referring now to Figures 1-3a, orbiting scroll member 56 and non-orbiting scroll
member 70 are illustrated in greater detail. Non-orbiting scroll member 70 is fixedly
secured to two-piece upper bearing housing 26 by a plurality of bolts 80 which prohibit
all movement of non-orbiting scroll member 70 with respect to upper bearing housing
26. Orbiting scroll member 56 is disposed between non-orbiting scroll member 70 and
upper bearing housing 26. Orbiting scroll member 56 can move radially as described
above in relation to the radially compliant drive for compressor 10. Orbiting scroll
member 56 can also move axially by means of a floating thrust seal 82 disposed within
annular recess 54.
[0017] Floating thrust seal 82 comprises an annular valve body 84, an inner lip seal 86
and an outer lip seal 88. Annular valve body 84 defines an inner face seal 90 and
an outer face seal 92 which are urged against end plate 60 of orbiting scroll member
56 by fluid pressure supplied to recess 54 through a plurality of passages 94 extending
through annular valve body 84. Inner lip seal 86 seals against an inner wall of recess
54, outer lip seal 88 seals against an outer wall of recess 54 and face seals 90 and
92 seal against end plate 60 of orbiting scroll member 56 to isolate recess 54 from
suction pressure refrigerant within shell 12. The design parameters for floating thrust
seal 82 are selected in such a way that, under internal pressurization, annular valve
body 84 stays in constant contact with end plate 60 or orbiting scroll member 56 by
means of face seals 90 and 92. The majority of the axial biasing load applied to orbiting
scroll member 56 is supplied by the refrigerant gas pressure within recess 54 rather
than by mechanical contact between face seals 90 and 92 and end plate 60 of orbiting
scroll member 56. This reduces mechanical friction and wear of face seals 90 and 92
and the corresponding surface of end plate 60 of orbiting scroll member 56. Pressurization
of recess 54 is achieved using one or more passages 96 which extend from an area of
end plate 60 open to recess 54 through end plate 60 and through scroll wrap 58 of
orbiting scroll member 56.
[0018] Referring now to Figure 3b, a biasing system in accordance with another embodiment
of the present invention is disclosed. Figure 3b illustrates floating thrust seal
82' which is the same as floating thrust seal 82 except that annular valve body 84
is replaced by a three piece annular body 84a, 84b and 84c.
[0019] Floating thrust seal 82' comprises annular valve bodies 84a, 84b and 84c, an inner
lip seal 86 and an outer lip seal 88. Annular valve body 84a defines an inner face
seal 90 and an outer face seal 92 which are urged against end plate 60 of orbiting
scroll member 56 by fluid pressure supplied to recess 54 through a plurality of passages
94 extending through annular valve body 84a. Inner lip seal 86 is located between
annular valve body 84a and 84b and it seals against an inner wall of recess 54, outer
lip seal 88 is located between annular valve body 84a and 84c and it seals against
an outer wall of recess 54 and face seals 90 and 92 seal against end plate 60 of orbiting
scroll member 56 to isolate recess 54 from suction pressure refrigerant within shell
12. The use of the three piece annular valve bodies 84a, 84b and 84c allows lip seals
86 and 88 to operate independently from each other. The design parameters for floating
thrust seal 82 are selected in such a way that, under internal pressurization, annular
valve body 84a stays in constant contact with end plate 60 or orbiting scroll member
56 by means of face seals 90 and 92. The majority of the axial biasing load applied
to orbiting scroll member 56 is supplied by the refrigerant gas pressure within recess
54 rather than by mechanical contact between face seals 90 and 92 and end plate 60
of orbiting scroll member 56. This reduces mechanical friction and wear of face seals
90 and 92 and the corresponding surface of end plate 60 of orbiting scroll member
56. Pressurization of recess 54 is achieved using one or more passages 96 which extend
from an area of end plate 60 open to recess 54 through end plate 60 and through scroll
wrap 58 of orbiting scroll member 56.
[0020] During orbiting motion of orbiting scroll member 56 with respect to non-orbiting
scroll member 70, the end of the one or more passages 96 extending through scroll
wrap 58 connects to one of the moving pockets defined by scroll wraps 58 and 72 by
means of a recess 98 which is machined into end plate 74 of non-orbiting scroll member
70. The location, size and shape of the one or more passages 96 and recess 98 will
determine the opening and closing of gas communication between the compressed gas
in the moving pocket and recess 54. In addition, the transition time of the pressure
equalization between the moving pocket and recess 54 is controlled by the location,
size and shape of the one or more passages 96 and recess 98. The timing of the opening
and closing in conjunction with the transition time can be selected such that it will
minimize excessive axial force applied to end plate 60 of orbiting scroll member 56
but at the same time the axial force will keep orbiting scroll member 56 in constant
contact with non-orbiting scroll member 70. Figure 4a illustrates the beginning of
the opening of communication, Figure 4b illustrates an opened communication and Figure
4c illustrates the closing of communication between recess 98 and one passage 96.
[0021] Keterring now to Figure 5, an axial pressure biasing system 110 is illustrated. During
the operation of compressor 10, suction gas is sucked into scroll members 56 and 70
where it is compressed and then discharged from discharge passage 76 through discharge
fitting 18 that extends through cap 14. Because the axial force from the compressed
gas is located primarily in the center of orbiting scroll member 56, and axial support
for orbiting scroll member 56 from floating thrust seal 82 is located at the periphery
of orbiting scroll member 56, end plate 60 of orbiting scroll member 56 experiences
bending such that the upper surface of end plate 60 becomes concave. At the same time,
due to the thermal field, orbiting scroll wrap 58 as well as non-orbiting scroll wrap
72 are experiencing thermal growth, with the higher growth being in the center of
scroll members 56 and 70. The lower surface of end plate 74 of non-orbiting scroll
member 70 also becomes concave due to the axial separating force from the compressed
gas in the moving pockets. However, gas pressure behind end plate 74 of non-orbiting
scroll member 70 can also influence the deflection of end plate 74.
[0022] Non-orbiting scroll member 70 is sealingly secured to end cap 14 using a seal 112.
Non-orbiting scroll member 70 and end cap 14 define a pressure chamber 114 which is
supplied intermediate pressurized gas from one or more of the moving pockets defined
by wraps 58 and 72 through a passage 116 extending through end plate 74. At a given
operating condition, determined by suction and discharge pressure, it is possible
to determine the value of gas pressure in pressure chamber 114. The gas pressure in
pressure chamber 114 influences the deflection of end plate 74 in such a way that
the tips of orbiting scroll wrap 58 as well as the tips of non-orbiting scroll wrap
72 will be as close to a uniform contact as possible. The necessary gas pressure to
achieve the uniform contact with the respective end plates 60 and 74 can be selected
by properly positioning passage 116 in end plate 74.
[0023] Referring now to Figures 6 and 7a-7c, a vapor injection system 120 in accordance
with the present invention is illustrated. The source for vapor injection is located
external to compressor 10 and it is supplied from a fluid line (not shown) which extends
through cap 14. Non-orbiting scroll member 70 defines a fluid injection port 122 to
which the fluid line is attached to supply the pressurized vapor to scroll members
56 and 70. Fluid injection port 122 is in communication with an axial passage 124
in orbiting scroll member 56. Axial passage 124 is in communication with a radial
passage 126 which is in turn in communication with a pair of axial passages 128 which
open into the moving fluid pockets defined by scroll wraps 58 and 72. In order to
achieve the necessary amount of vapor introduced into the moving pockets, opening
and closing of communication between port 122 and passage 124 must be controlled.
The opening of port 122 to passage 124 should begin just after the moving pocket is
formed by being sealed from the suction area of compressor 10. The closing of port
122 to passage 124 should happen after approximately ninety degrees of rotation of
orbiting scroll member 56. Because of the relative orbiting motion of orbiting scroll
member 56 with respect to non-orbiting scroll member 70, the proper selection of relative
locations of port 122, passage 124 and passages 128 make it possible to control the
opening and closing of vapor injection system 120. Opening and closing of vapor injection
system 120 to provide vapor to the moving pockets can be achieved by either lowering
and uncovering passages 128 on end plate 60 of orbiting scroll member 56 by scroll
wrap 72 of non-orbiting scroll member or by opening and closing communication between
port 122 and passage 124 or by a combination of both.
[0024] Figure 7a illustrates scroll members 56 and 70 corresponding to the point where the
moving pockets defined by scroll wraps 58 and 72 are initially sealed off from the
suction area of compressor 10. Communication between port 122 and passage 124 is just
starting to take place and passages 128 are just beginning to be uncovered by scroll
wrap 72. Figure 7b illustrates scroll members 56 and 70 corresponding to the position
forty-five degrees of rotation after the initial sealing point illustrated in Figure
7a. Port 122 is open to passage 124 and passages 128 are not covered by scroll wrap
72 to provide for vapor injection. Figure 7c illustrates scroll members 56 and 70
corresponding to the position ninety degrees of rotation after the initial sealing
paint illustrated in Figure 7a. Port 122 has just closed communication with passage
124 to stop vapor injection by vapor injection system 120.
[0025] Referring now to Figures 8 and 9, a scroll compressor 210 in accordance with another
embodiment of the present invention is illustrated. Scroll compressor 210 is the same
as scroll compressor 10 but scroll compressor 210 includes an optional oil injection
system 212. Scroll compressor 210 includes a non-orbiting scroll member 70' which
replaces non-orbiting scroll member 70 and a two-piece upper bearing housing 26' which
replaces two-piece upper bearing housing 26. Non-orbiting scroll member 70' is the
same as non-orbiting scroll member 70 except that non-orbiting scroll member 70' defines
an oil pressure passage 214 and an oil pressure groove 216. Upper bearing housing
26' is the same as upper bearing housing 26 except that upper bearing housing 26'
defines an oil supply passage 218.
[0026] Oil injection system 212 injects oil into the moving chambers defined by scroll wraps
56 and 72 for cooling and lubrication through passage 94 and the one or more passages
96. While passages 94 and 96 are illustrated as being used for oil injection, it is
within the scope of the present invention to have additional or other dedicated oil
injection ports if desired. Once oil is injected into the moving pockets, it is discharged
together with the compressed gas and then separated from the compressed gas in an
external oil separator (not shown). The separated oil is then cooled and reinjected
into the moving pockets of compressor 210.
[0027] A source of high pressure oil or high pressure sump 228 is connected through cap
14 to oil pressure passage 214 to provide high pressure oil to annular recess 54 and
floating thrust seal 82. In order to control the pressure of the supplied oil, an
external oil pressure regulator 230 is utilized. Also, in order to provide the necessary
feed back for regulator 230, oil groove 216 and oil pressure passage 214 are connected
through cap 14 to regulator 230. When orbiting scroll member 56 is in tight contact
with non-orbiting scroll member 70', groove 216 is sealed from the suction area of
compressor 210. However, when scroll axial separation takes place, groove 216 opens
to the suction area of compressor 210 to provide a leak path.
[0028] Referring now to Figure 9, oil pressure regulator 230 comprises a housing 232 and
a differential piston 234. On the left side of piston 234 as shown in Figure 9, there
is a hydrostatic thrust bearing chamber 236 and a lubrication groove sensing chamber
238. Lubrication groove sensing chamber 238 is connected to oil groove 216 through
oil pressure passage 214. Lubrication groove sensing chamber 238 is also connected
to high pressure oil sump 228 through a metering orifice 240. To the right of piston
234 as shown in Figure 9, there is an adjustment piston 242 which is threaded into
housing 232. Adjustment piston 242 can be used to adjust the preload of springs 244
which urge piston 234 to the left as shown in Figure 9. Adjustment piston 242 together
with piston 234 form a chamber 246 and a chamber 248.
[0029] During operation chamber 246 is connected to high pressure oil sump 228 and chamber
248 to high pressure oil sump 228 and chamber 248 is connected to the suction side
of compressor 210. There is a circular groove 250 in piston 234 which is connected
by a passage 252 to hydrostatic thrust bearing chamber 236. A radial passage 254 through
housing 232 is also connected to the suction side of compressor 210. A second radial
passage 256 through housing 232 is connected to high pressure sump 228. During operation,
the position of piston 234 is determined by the balance of forces in chambers 236,
238, 246 and 248 and the forces exerted by springs 244. The pressure in chamber 236
is controlled by oil leakage from groove 250 to/from radial passages 254 and 256.
This leakage depends on the position of groove 250 relative to the openings of passages
254 and 256. Differential piston diameters, as well as other design parameters, are
selected in such a way that the controlled pressure in chamber 236 becomes a proper
combination of suction and discharge pressures and spring force resulting in the best
possible pressure within annular recess 54 reacting on orbiting scroll member 56 and
floating thrust seal 82 to provide the appropriate amount of biasing for orbiting
scroll member 56 for the efficient operation of compressor 210. When scroll members
56 and 70' are in tight contact, the oil pressure in circular groove 216 and chamber
238 are close to the design pressure. However, in the event of scroll axial separation,
oil leakage from groove 216 to the suction portion of compressor 210 will result in
a drop of pressure in groove 216 and chamber 238 due to the presence of metering orifice
240. This changes the force balance equilibrium on piston 234 resulting in groove
250 aligning with passage 256 increasing the oil pressure within chamber 236 by connecting
chamber 236 to high pressure sump 228 through passage 252, groove 250 and passage
256. This increased oil pressure is supplied from chamber 236 to annular recess 54
resulting in an increase in the clamping force in order to bring the scrolls back
together. With the scrolls back together, the pressure within groove 216 and chamber
238 will return to the pressure of high pressure sump 228 which will move piston 234
to the right as shown in Figure 9 until groove 250 aligns with passage 254 to bleed
the increased pressure within chamber 236 to the suction area of the compressor through
passage 252, groove 250 and passage 254. This brings the pressure within chamber 236
and thus annular recess 54 back to the design pressure.
[0030] Referring now to Figure 10, a scroll compressor 310 in accordance with another embodiment
of the present invention is illustrated. Scroll compressor 310 is the same as scroll
compressor 10 but scroll compressor 310 incorporates a different biasing system for
the orbiting scroll member.
[0031] Compressor 310 comprises generally cylindrical hermetic shell 12 having welded at
the upper end thereof cap 14 and at the lower end thereof the plurality of mounting
feet 16. Cap 14 is provided with refrigerant discharge fitting 18. Other major elements
affixed to shell 12 include lower bearing housing 24 that is suitably secured to shell
12 and two piece upper bearing housing 26 suitably secured to lower bearing housing
24.
[0032] Drive shaft or crankshaft 28 having eccentric crank pin 30 at the upper end thereof
is rotatably journaled in bearing 32 in lower bearing housing 24 and second bearing
34 in upper bearing housing 26. Crankshaft 28 has at the lower end the relatively
large diameter concentric bore 36 that communicates with radially outwardly inclined
smaller diameter bore 38 extending upwardly therefrom to the top of crankshaft 28.
The lower portion of the interior shell 12 defines oil sump 40 that is filled with
lubricating oil to a level slightly above the lower end of rotor 42, and bore 36 acts
as a pump to pump lubricating fluid up crankshaft 28 and into bore 38 and ultimately
to all of the various portions of the compressor that require lubrication.
[0033] Crankshaft 28 is rotatively driven by the electric motor including stator 46, winding
48 passing therethrough and rotor 42 press fitted on crankshaft 28 and having upper
and lower counterweights 50 and 52, respectively.
[0034] The upper surface of upper bearing housing 26 is provided with annular recess 54
above which is disposed an orbiting scroll member 356 having the usual spiral vane
or wrap 358 extending upward from an end plate 360. Projecting downwardly from the
lower surface of end plate 360 of orbiting scroll member 356 is a cylindrical hub
having a journaled bearing 362 therein and in which is rotatively disposed drive bushing
64 having an inner bore in which crank pin 30 is drivingly disposed. Crank pin 30
has a flat on one surface that drivingly engages a flat surface (not shown) formed
in a portion of the bore to provide a radially compliant driving arrangement, such
as shown in Assignee's U.S. Letters Patent
4,877,382. Oldham coupling 68 is also provided positioned between orbiting scroll member 356
and upper bearing housing 26 and keyed to orbiting scroll member 356 and upper bearing
housing 26 to prevent rotational movement of orbiting scroll member 356.
[0035] A non-orbiting scroll member 370 is also provided having a wrap 372 extending downwardly
from an end plate 374 that is positioned in meshing engagement with wrap 358 of orbiting
scroll member 356. Non-orbiting scroll member 370 has a centrally disposed discharge
passage 376 that communicates with discharge fitting 18 which extends through end
cap 14.
[0036] Non-orbiting scroll member 370 is fixedly secured to two-piece upper bearing housing
26 by plurality of bolts 80 which prohibit all movement of non-orbiting scroll member
370 with respect to upper bearing housing 26. Orbiting scroll member 356 is disposed
between non-orbiting scroll member 370 and upper bearing housing 26. Orbiting scroll
member 356 can move radially as described above in relation to the radially compliant
drive for compressor 310. Orbiting scroll member 356 can also move axially by means
of a floating thrust seal 382 disposed within annular recess 54.
[0037] Floating thrust seal 382 comprises a pair of annular valve bodies 384 with one annular
body 384 sealingly engaging the interior wall of recess 54 at 386 and the other annular
body 384 sealingly engaging the exterior wall of recess 54 at 388. Annular valve bodies
384 define an inner face seal 390 and an outer face seal 392 which are urged against
end plate 360 of orbiting scroll member 356 by fluid pressure supplied to recess 54.
The seal at 386 seals against the inner wall of recess 54, the seal at 388 seals against
the outer wall of recess 54 and face seals 390 and 392 seal against end plate 360
of orbiting scroll member 356 to isolate recess 54 from suction pressure refrigerant
within shell 12. The design parameters for floating thrust seal 382 are selected in
such a way that, under internal pressurization, annular valve bodies 384 stay in constant
contact with end plate 360 of orbiting scroll member 356 by means of face seals 390
and 392. The majority of the axial biasing load applied to orbiting scroll member
356 is supplied by the refrigerant gas pressure within recess 54 rather than by mechanical
contact between face seals 390 and 392 and end plate 360 of orbiting scroll member
356. This reduces mechanical friction and wear of face seals 390 and 392 and the corresponding
surface of end plate 360 of orbiting scroll member 356. While not illustrated in Figure
10, pressurization ot recess 54 is achieved using one or more passages 96 which extend
from an area of end plate 360 open to recess 54 through end plate 360 to one or more
of the compression chambers formed by wraps 358 and 372 as shown in Figures 1-4c.
Also, scroll compressor 10 can include the optional oil injection system 212 illustrated
above for compressor 210.
[0038] During orbiting motion of orbiting scroll member 356 with respect to non-orbiting
scroll member 370, a plurality of passages 396 which extend through end plate 360
control the pressure within a recess 398. The end of each passage 396 extending through
end plate 360 connects to one of a plurality of recesses 398 which are machined into
end plate 374 of non-orbiting scroll member 370. The location, size and shape of passage
396 and recess 398 will determine the opening and closing of gas communication between
the compressed gas in the suction area of scroll compressor 310 and recess 398 as
well as the opening and closing of gas communication between recess 54 and recess
398. In addition, the transition time of the pressure equalization between the suction
area of scroll compressor 310 and recess 398 and the transition time of the pressure
equalization between recess 54 and recess 398 is controlled by the location, size
and shape of passage 396 and recess 398. The timing of the opening and closing in
conjunction with the transition time can be selected such that it will minimize excessive
axial force applied to end plate 360 of orbiting scroll member 356 but at the same
time the axial force will keep orbiting scroll member 356 in constant contact with
non-orbiting scroll member 370.
[0039] Scroll compressors create a contingent axial force that tries to separate the two
mating scrolls due to the compression process. This force changes in a revolution
with ten to thirty percent of the fluctuation depending on the operating condition.
To overcome the separating force and hold the mating scrolls together, a constant
gas pressure is applied from the back side of the orbiting scroll member by using
a sealing system which is typically provided on a stationary part of the scroll compressor.
In order to keep the scroll members together at all times with the constant pressure
acting against the fluctuating separating force, the backpressure that creates the
holding force must be equal to or more than the peak value of the fluctuating force
creating an excessive pressure. As a result, the excessive force will be exerted on
the mating axial surfaces of the sealing system. This excessive force causes frictional
losses that deteriorates the efficiency of the compressor.
[0040] There is another circumstance which requires an unwanted excessive force. This is
due to the presence of the "scroll particular" over-turning moment which is schematically
illustrated in Figures 11a-11c. Since the separation force F
SP and the holding force F
HOLD are separately placed by a half of the orbiting radius R
OR, the centroid of the excessive force F
TH needs to occur at the opposite side of the axis (shown in X) in order to balance
out the moment from the two forces F
SP and F
HOLD. As seen in Figure 11b, the force balance in the axial direction can be represented
by the following equation [1].
[0041] The location X illustrated in Figure 11b becomes off setting from the central axis
with which the holding force F
HOLD gets close to the separation force F
SP to eliminate the excessive force and its location can be represented by the following
equation [2].
[0042] Substituting equation [1] into equation [2] gives us the location for X which can
be represented by the following equation [3].
[0043] The location of F
TH is also affected by the other moment balance in the tangential plane shown in the
following equation [4].
[0044] This equation can be written as
and substituting equation [1] in this equation gives us the position for Y.
[0045] As indicated, the Y location also becomes off from the central axis by minimizing
the excessive force (F
HOLD-F
SP). For most of scroll compressors, the F
TH positions near the tangential line, which is extended from the center of the orbiting
scroll toward the rotation direction of the orbit. As the tangential and radial axes
rotate, F
TH moves along the tangential axis resulting in drawing a closed loop trajectory as
illustrated in Figure 12 by the dashed line. If no axial surface is provided between
the mating scroll members at the location of F
TH, the orbiting scroll member will tilt over and thus result in the scroll compressor
being inoperative. Therefore, the excessive force is allowed to be reduced only within
the range of which F
TH does not go across the outer edge of the axial surface between the mating scrolls.
[0046] A typical approach to overcome such excessive force is to widen the axial thrust
area in order to extend the outer edge of the axial surface as well as to reduce the
contact force per unit area. With this approach, however, it brings about the compressor
shell diameter being larger which is against the market demand for miniaturization.
In addition, lubrication of this increased surface area presents additional problems.
[0047] The present invention addresses this issue by increasing and decreasing the fluid
pressure within recess 398 which creates a pressure biasing chamber during the cycle
of rotation in order to counteract the circumferential movement of F
TH. The increasing and decreasing of the fluid pressure within recess 398 is described
above where recess 398 is cyclically placed in communicated with the suction area
of compressor 310 and the fluid pressure within recess 54.
[0048] Figures 13-18 illustrate the positional and geometrical information about the plurality
of passages 396 in end plate 360, the plurality of recesses 398 formed in end plate
374 and an axial sealing surface 400 of annular recess 54 provided at the backside
of end plate 360.
[0049] Preferably, four passages 396a-d are arranged circumferentially around end plate
360 at a ninety degree interval at a diameter of C
BH from the center of orbiting scroll member 356. The diameter D
BH for each passage 396 is preferred, but not limited to be matched to a seal width
of outer face seal 392. Preferably four recesses 398a-d are arranged circumferentially
around end plate 374 at a diameter C
GR. The four recesses 398 are not interconnected with each other and thus they can each
be treated as an independent volume. The depth of each recess t
GR is preferred, but not limited to be considerably small such as less than a millimeter.
Recesses 398 are arranged at ninety degree interval on diameter C
GR from the center of non-orbiting scroll member 370. Recesses 398 are preferred but
are not limited for each to have a width L
GR which is equal to or greater than twice the orbiting radius R
OR. The diameter C
GR is preferred to be the same size of diameter C
BH of passage 396. Also, the diameter C
GR is preterred, but not limited to be the same as the diameter C
SEAL of outer face seal 392. The matching of diameters C
GR and C
SEAL permit the fabrication of the plurality of passages 396 by a simple vertical drilling
operation.
[0050] An angular orientation of the four recesses 398 is preferred, but not limited to
be arranged so that the symmetric axis of each recess coincides with the radial direction
of a respective passage 396.
[0051] Figures 19a-19d show the positional relationship between the passages 396, the recesses
398 and the outer sealing surface of outer face seal 392 at each ninety degree rotation
of orbiting scroll member 356 with respect to non-orbiting scroll member 370. The
relative position of each passage 396 and the outer sealing surface of outer face
seal 392 are successively changed as the center O
OS of orbiting scroll member 356 orbits on the orbiting circle C
OR around the center O
FS of non-orbiting scroll member 370. Each passage 396 comes across the axial sealing
surface of outer face seal 392 twice during one revolution of orbiting scroll member
356. Thus, the bottoms of passages 396 are repeatedly and alternately exposed to high
pressure and low pressure refrigerant environments. The exposure of each passage 396
becomes phase-delayed by ninety degrees such that the exposures occur on respective
passages 396 one after another during the orbital motion.
[0052] The upper end of each passage 396 is in communication with a respective recess 398
at all times. Therefore, the pressures of fluid within recesses 398 fluctuates during
each revolution of orbiting scroll member 356 as the result of the alternate exposure
of passages 396 to the high and low pressures of the refrigerant environment. A typical
pattern of the pressure fluctuation in each recess 398 is shown in Figure 20. The
pressure increases when passage 396 is exposed to the high pressure environment and
it decreases when it is exposed to the low pressure environment. Although the rate
of the increase and the decrease of the pressure within each recess 398 is affected
by the volume of the recess and the flow resistance of passage 396, the peak pressure
always appears at the end of the exposure of passage 396 to the high pressure and
the bottom pressure occurs at the end of the exposure of passage 396 to the low pressure.
This is illustrated in Figure 20 where the solid line indicates recess pressure for
a large volume recess 398 or a high flow resistance passage 396 and the dashed line
indicates recess pressure for a small volume recess 398 or a low flow resistance passage
396.
[0053] In the crank position illustrated in Figure 19a, passage 396a is located at the ending
position of the exposure to the inside of recess 54 which holds a higher pressure
than the suction area of scroll compressor 310. Thus, at this crank position, the
pressure within recess 398a reaches its maximum, generating a peak force to counteract
the excessive force F
TH, which is generated by the overturning moment. Since the pressure within recess 398
is uniform, the location of the force should be represented by the centroid of the
recesses axial area, which is shown in Figure 16 as F
GRA.
[0054] As illustrated in Figure 12, the excessive force F
TH always appears near the tangential line, which is extended from the center of orbiting
scroll member 356 toward the rotational direction of orbit. As seen in Figure 16,
the centroid of the counteracting force F
GRA is located close to F
TH. Providing the counteracting force F
GRA close the F
TH will negate most of the excessive force F
TH and prevent a residual moment due to the presence of a minimum distance between F
GRA and F
TH.
[0055] As the orbital motion proceed from the crank position illustrated in Figure 19a to
that illustrated in 19b, passage 396a comes across the outer sealing surface of outer
face seal 392 and will be exposed to the suction area of scroll compressor 310. The
pressure within recess 398a will start to decrease and thus reduce the counteracting
from recess 398a. On the next recess 398b, however, the respective passage 396b is
approaching the end position of the exposure to the inside of pressurized recess 54
which is increasing the pressure within recess 398b. In the middle position between
Figures 19a and 19b, therefore, both recesses 398a and 398b hold an intermediate pressure
which generates intermediate counteracting forces at both F
GRA and F
GRB. These two forces can also be represented by the centroid of the two recesses which
is located between the two centroids of the two recesses. The location of the counteracting
force therefore moves circumferentially in the direction of the orbital motion and
follows the movement of F
TH which is illustrated in Figure 12 by the dashed line. Figures 19c and 19d each illustrate
an additional ninety degrees of orbital motion.
[0056] The passages 396a-d are illustrated as vertical and straight on the premise of which
diameter of the concentric circles of recesses C
GR matches with the diameter of the sealing face of outer face seal 392. This premise
sometimes cannot be met due to layout restrictions in relation to the other components.
Passages 396 can be replaced with passage 396' illustrated in Figure 21 so that the
bottom of passages 396' are still exposed to the inside and outside of recess 54 repeatedly
and alternately. As illustrated in Figure 22, the angular orientation of recesses
398 can be modified within forty-five degrees from the case of the preferred embodiment
with the symmetric axis of each groove coinciding with the radial direction of the
respective passage 396. This will allow shifting of the centroid of the respective
recesses 398 in the circumferential direction and further minimizing the distance
between the excessive force F
TH and the counteracting force F
GR. While Figure 22 illustrated modification in a clockwise direction, it is within
the scope of the present invention to modify recesses 398 in a counter-clockwise direction
if desired.
[0057] Referring now to Figures 23 and 24, a scroll compressor 410 in accordance with the
present invention is illustrated. Scroll compressor 410 is the same as scroll compressor
10 but scroll compressor 410 incorporates a hydrostatic thrust bearing. Compressor
410 comprises generally cylindrical hermetic shell 12 having welded at the upper end
thereof cap 14 and at the lower end thereof plurality of mounting feet 16. Cap 14
is provided with refrigerant discharge fitting 18. Other major elements affixed to
shell 12 include lower bearing housing 24 that is suitably secured to shell 12 and
two piece upper bearing housing 26 suitably secured to lower bearing housing 24.
[0058] Drive shaft or crankshaft 28 having eccentric crank pin 30 at the upper end thereof
is rotatably journaled in bearing 32 in lower bearing housing 24 and second bearing
34 in upper bearing housing 26. Crankshaft 28 has at the lower end the relatively
large diameter concentric bore 36 that communicates with radially outwardly inclined
smaller diameter bore 38 extending upwardly therefrom to the top of crankshaft 28.
The lower portion of the interior shell 12 defines oil sump 40 that is filled with
lubricating oil to a level slightly above the lower end of rotor 42, and bore 36 acts
as a pump to pump lubricating fluid up crankshaft 28 and into bore 38 and ultimately
to all of the various portions of the compressor that require lubrication.
[0059] Crankshaft 28 is rotatively driven by the electric motor including stator 46, winding
48 passing therethrough and rotor 42 press fitted on crankshaft 28 and having upper
and lower counterweights 50 and 52, respectively.
[0060] The upper surface of upper bearing housing 26 is provided with annular recess 54
above which is disposed an orbiting scroll member 456 having the usual spiral vane
or wrap 458 extending upward from an end plate 460. Projecting downwardly from the
lower surface of end plate 460 of orbiting scroll member 456 is a cylindrical hub
having a journaled bearing 462 therein and in which is rotatively disposed drive bushing
64 having an inner bore in which crank pin 30 is drivingly disposed. Crank pin 30
has a flat on one surface that drivingly engages a flat surface (not shown) formed
in a portion of the bore to provide a radially compliant driving arrangement, such
as shown in Assignee's U.S. Letters Patent
4,877,382, the disclosure of which is hereby incorporated herein by reference. Oldham coupling
68 is also provided positioned between orbiting scroll member 456 and upper bearing
housing 26 and keyed to orbiting scroll member 456 and upper bearing housing 26 to
prevent rotational movement of orbiting scroll member 456.
[0061] A non-orbiting scroll member 470 is also provided having a wrap 472 extending downwardly
from an end plate 474 that is positioned in meshing engagement with wrap 458 of orbiting
scroll member 456. Non-orbiting scroll member 470 has a centrally disposed discharge
passage 476 that communicates with discharge fitting 18 which extends through end
cap 14.
[0062] Non-orbiting scroll member 470 is fixedly secured to two-piece upper bearing housing
26 by the plurality of bolts 80 which prohibit all movement of non-orbiting scroll
member 470 with respect to upper bearing housing 26. Orbiting scroll member 456 is
disposed between non-orbiting scroll member 470 and upper bearing housing 26. Orbiting
scroll member 456 can move radially as described above in relation to the radially
compliant drive for compressor 410. Orbiting scroll member 456 can also move axially
by means of a floating thrust seal 482 disposed within annular recess 54.
[0063] Floating thrust seal 482 comprises a pair of annular bodies 484 with one annular
body 484 sealingly engaging the inner wall of recess 54 at 486 and the other annular
body 484 sealingly engaging the exterior wall of recess 54 at 488. Annular valve bodies
484 define an inner face seal 490 and an outer face seal 492 which are urged against
end plate 460 of orbiting scroll member 456 by fluid pressure supplied to recess 54.
The seal at 486 seals against the inner wall of recess 54, the seal 488 seals against
the outer wall of recess 54 and face seals 490 and 492 seal against end plate 460
of orbiting scroll member 456 to isolate recess 54 from suction pressure refrigerant
within shell 12. The design parameters for floating thrust seal 482 are selected in
such a way that, under internal pressurization, annular valve bodies 484 stay in constant
contact with end plate 460 or orbiting scroll member 456 by means of face seals 490
and 492. The majority of the axial biasing load applied to orbiting scroll member
456 is supplied by the refrigerant gas pressure within recess 54 rather than by mechanical
contact between face seals 490 and 492 and end plate 460 of orbiting scroll member
456. This reduces mechanical friction and wear of face seals 490 and 492 and the corresponding
surface of end plate 460 of orbiting scroll member 456. Pressurization of recess 54
is achieved using the one or more passages 96 which extends from an area of end plate
460 open to recess 54 through end plate 460 and through scroll wrap 458 of orbiting
scroll member 456.
[0064] Scroll compressor 410 incorporates a hydrostatic thrust bearing 500 or non-orbiting
scroll member 470. Hydrostatic bearing 500 is located at a thrust surface 502 of non-orbiting
scroll member 470 which mates with end plate 460 of orbiting scroll member 456. This
positions hydrostatic bearing 500 exterior to non-orbiting scroll wrap 472. Hydrostatic
bearing 500 comprises one or more recesses 504 disposed on thrust surface 502, one
or more throttling devices 506 such as orifices, tubes, valves, capillaries or other
throttling devices known in the art, a high pressure oil source 508 and one or more
oil passages 510 that connect high pressure oil source 508 to one or more recesses
504. An oil-separator 512 can be used for high pressure oil source 508 and as illustrated
in Figure 23, oil-separator 512 is located at the discharge end of scroll compressor
410.
[0065] As described above, scroll compressor can create a contingent axial force by its
compression mechanism which tries to separate the two mating scrolls. This force changes
during a revolution of the orbiting scroll member with ten to thirty percent of the
fluctuation depending on the operating condition. To overcome the separating force
and hold the mating scroll members together, a constant back pressure is generally
applied from a side of the non-orbiting scroll member or from a side of the orbiting
scroll member. In order to keep the scroll members together with the constant back
pressure against the fluctuating separating force, the back pressure that creates
a force equal to or more than the peak value of the fluctuating force is chosen. As
a result, the excessive clamping force at the time of other than when the peak force
occurs will be applied to the scroll members resulting in mechanical loss. This loss
becomes more significant if the scroll compressor creates a large axial force relative
to the useful work output (tangential force) such as a scroll compressor for CO
2 refrigerant.
[0066] Preferably four separate recesses 504a-d are provided on thrust surface 502 of non-orbiting
scroll member 470. Recesses 504a-d are located circumferentially to surround scroll
wrap 472. By using separate recesses 504a-d, the capability to carry the eccentric
bias-load which scroll members normally generate will be enhanced. Each recess has
its own throttling device 506 to provide each recess 504 with its own independent
oil carrying capacity. This feature is also necessary for the eccentric load. The
land of each recess 504 is adjusted in height to be flush with the tip surface of
non-orbiting scroll wrap 472.
[0067] A common oil passage 514 connects to each recess 504 through a high pressure oil
line 516 connected to oil separator 516. As detailed above, a constant back pressure
from recess 54 is applied to end plate 460 of orbiting scroll member 456.
[0068] Hydrostatic thrust bearing 500 will provide rigidity to the load carrying capacity
against the clearance between the two mating surfaces, end plate 460 and thrust surface
502. Hydrostatic thrust bearing 500 will carry additional load as the clearance between
the two surfaces decrease. When there is excessive force applied to orbiting scroll
member 456 from the fluid pressure within recess 54, orbiting scroll member 456 comes
closer to non-orbiting scroll member 470. Hydrostatic thrust bearing 500 will generate
an increased reaction force as orbiting scroll member 456 comes closer to non-orbiting
scroll member 470. Both the biasing force and the reaction force will balance out
at a certain clearance where orbiting scroll member 456 will stop its axial movement.
As a result, orbiting scroll member 456 stays in a floating state with respect to
non-orbiting scroll member 470 not transferring forces between the tips of scroll
wraps 458, 472 and end plates 474, 460, respectively. This floating state of orbiting
scroll member 456 eliminates the friction loss between the scroll tips and the end
plates.
[0069] This reduction becomes more of a significant factor when the biasing load created
by the pressurized fluid in recess 54 is large. This is especially true for scroll
compressors that create significant fluctuation of the separating force such as the
ones for CO
2 refrigerant. Hydrostatic thrust bearing 500 accommodates this fluctuating force by
allowing a change in the floating position of orbiting scroll member 456. If this
change in the floating position becomes too large, the performance of the scroll compressor
may be degraded due to leakage of the compressed gas between adjacent scroll pockets.
If the change in the floating position becomes too large, the prevention of gas leakage
can be accomplished by designing recesses 504 and throttling devices 506 to realize
the maximum rigidity which will then bring about the minimum change in the floating
position in relation to the fluctuation of the load.
[0070] Hydrostatic thrust bearing 500 can be intentionally designed to be, more or less,
too small in its load carrying capacity against the separating force. Hydrostatic
thrust bearing 500 will then carry a part of the separation force at the two mating
scroll members in contact. Although, in this design, hydrostatic bearing 500 does
not completely eliminate the tip friction, it still reduces the friction drastically
by receiving axial stress at the tip of the scroll.
[0071] While the present invention is illustrated with hydrostatic thrust bearing being
on the non-orbiting scroll member with an axially movable orbiting scroll member,
hydrostatic bearing 500 can be incorporated into an orbiting scroll member that does
not move axially but which is mated with an axially movable non-orbiting scroll member.
[0072] The description of the invention is merely exemplary in nature.